diff --git a/addons/mail/static/src/css/mail.css b/addons/mail/static/src/css/mail.css
index 45263d84a63..abc954fef0b 100644
--- a/addons/mail/static/src/css/mail.css
+++ b/addons/mail/static/src/css/mail.css
@@ -41,7 +41,7 @@
     padding: 2px;
 }
 
-.openerp div.oe_mail_thread_subthread img {
+.openerp div.oe_mail_thread_subthread img.oe_mail_msg_image {
     width: 30px;
     height: 30px;
 }